1. Field of the Invention
This invention relates to a water-soluble or hydrophilic sulfonation product of a conjugated diene, a polymer of the sulfonation product and a dispersion of a dispersoid in an aqueous medium in which the sulfonation product or the polymer is used as a dispersing agent.
2. Discussion of the Background
Known water-soluble and/or hydrophilic monomers are those having a carboxyl group such as acrylic acid, methacrylic acid and the like; those having a sulfonic acid group such as allylsulfonic acid, vinylsulfonic acid and the like; etc.
Also, sodium, potassium and lithium salts of the above monomers are known to be radically polymerizable.
Water-soluble polymers or hydrophilic polymers can be produced by polymerizing the above monomers or their salts alone or copolymerizing them with other monomers, and are used widely in industry. For example, polyacrylic acids are used as a dispersing agent for calcium carbonate and partially crosslinked products thereof are used as water-absorbent gels.
Moreover, there are many cases in which acrylic acid and/or methacrylic acid is copolymerized with other vinyl monomers for the purpose of modifying rubbers and resins. Further, acrylic acid and/or methacrylic acid is copolymerized with latexes for modifying the latter.
However, these acidic monomers such as acrylic acid, methacrylic acid and the like are weakly acidic though rich in radical-polymerizability, and the polymers obtained therefrom are disadvantageous in that their emulsifying powers are weak when they are used as surfactants.
On the other hand, vinylsulfonic acid, allylsulfonic acid, methacrylsulfonic acid obtained by reacting isobutylene with sulfur trioxide, and the like are alkenyl monomers having a strongly acidic sulfonic acid group, and polymers thereof are strongly acidic and excellent in emulsifying power. However, the monomers per se are poor in radical-polymerizability and give only a low polymer yield and the polymers produced therefrom have only a low molecular weight.
In addition, there have been developed monomers having a sulfonic acid group, such as styrenic monomers, for example, sodium p-styrenesulfonate and the like (e.g., Spinomer, a trade name of Toso Co., Ltd.) and methacrylic monomers represented by the formula: ##STR2## (e.g., Eleminol RS-30, a trade name of Sanyo Kasie K. K.).
These monomers have a large molecular weight and a small sulfonic acid group content per unit weight though they are strongly acidic and excellent radical-polymerizability. In addition, the synthesis of the monomers is effected via many steps, and hence, the production process is complicated and expensive.
Therefore, the ion-exchange capacity of the polymer obtained therefrom is low and the commercial productivity of the polymer is inferior and the production cost thereof is high. Thus, the uses thereof are inevitably limited.